'I'm leaving the old Zac Efron behind. It was a long time coming'

Five years ago, you couldn’t move for Zac Efron’s face: on billboards, posters and pencil cases from South Korea to South Kensington, there he was, grinning mawkishly. It was all down to a phenomenon called High School Musical, a precursor to Glee, which started with a chaste 2006 Disney TV film about an all-singing sports star (Zac, then 18) wooing the pretty swot, played by Vanessa Hudgens. The second TV film was released in 2007 and the third made it into cinemas in 2008, earning its biggest star nearly £2 million. But Justin Bieber he is not; being the world’s teen-idol-in-chief just didn’t cut it.

‘I was seeing so much of my face everywhere that I started to hate that guy,’ he admits. ‘It was over-saturation. And “heart-throb” isn’t tangible. When you earn that title... at best, it’s what? A fleeting thing. It all used to make me sad. I couldn’t handle it.’ His awards (Kids’ Choice and Teen Choice, a sort of tween BAFTA) are conspicuously not on display at his family’s home on the central Californian coast or his £1 million home in the Hollywood Hills, which he describes as ‘clean, modern, simple’. ‘I hid them in the garage next to the clothes we were donating to charity. I wanted awards for nailing a scene, for that rush.’

It’s only now, aged 24, that Zac is realising how much harder it is to set yourself up as an actor post life as a teen idol (it took fellow teen star Ryan Gosling more than ten years of graft to get his Oscar nomination, for Half Nelson in 2007) and to recognise the price of that level of teenage stardom. ‘I’ve missed out on so much. I’ve said those words to my parents and that thought runs through my head,’ he sighs. University for a start. ‘I would be studying marine biology or something to do with the outdoors.’ He told Vanity Fair in 2009 that he never sought fame and had been perfectly happy with his typical teenage life: skateboarding, listening to music and going to the cinema. All these things he had to give up at 18 (although he had concrete floors put in his home so at least he can skateboard, albeit privately).

Now when he’s feeling lost, or like a prisoner due to the incessant paparazzi outside his window, he reaches for the only thing he has in common with mid-twenties Californians: an iPhone. ‘There’s this meditation app. It sounds witchdoctory, but meditation has really helped me when I’m going to that dark “troubled actor” area. Just sitting back and taking deep breaths helps me with confidence. Clearing my head for a few moments a day is vital.’ He also relaxes by taking pictures: ‘I love being outside, and I love photography, especially working with vintage film cameras.’

Zac has a brace of more adult roles under his belt since the High School Musical trilogy ended: Me and Orson Welles, opposite Claire Danes, in which he played an actor working for a young Welles, and Charlie St Cloud, in which he played a grieving brother who still engages daily with his dead sibling. But his latest film, The Lucky One, isa significantly more mature turn. Zac plays Logan, a traumatised Marine on leave from Afghanistan, in this adaptation of Nicholas Sparks’ novel, directed by Scott Hicks, who won an Oscar in 1997 for Shine. Zac threw himself into the role, Method-actor style, gaining muscle and eventually dead-lifting 26 stone (twice his bodyweight) after a six-month training camp. ‘I’ve never pushed myself to those sorts of limits before. It became a rush to see what I could accomplish. I feel I’m leaving the old version of Zac behind. It was a long time coming.’

The soldiers he met during his research at Camp Pendleton, the US Marine Corps’ West Coast base south of LA, weren’t so sure that this all-singing, all-dancing teen star could play one of them convincingly. ‘Some of them asked: “What are you doing?” Who could blame them? If you’d asked me in the days of High School Musical if I was ever going to play an army sergeant, I’d have f***ing laughed. So honestly, when I first met those guys, I’d never been more afraid in my entire life. They were real men’s men. I just wasn’t like that.’

In 2002 Zac won his first TV role in The Avengers director Joss Whedon’s series Firefly and a year later, a more prominent one on ER (playing a hysterical sobbing teenager who’d been shot and subsequently died). By 2005 he was cast in the seaside drama Summerland as the boyfriend of one of the three orphaned siblings, alongside True Blood’s Ryan Kwanten. He stayed in school, living at home with his mum Starla, power-plant-engineer father David and younger brother Dylan. After attending his high school prom, Zac left school and normality behind when he landed the role of High School Musical’s Troy.

During the first film, he and Vanessa Hudgens, his co-star one year his junior, started dating but, like Kristen Stewart and Robert Pattinson, the young lovers were advised to deny their relationship because some publicist decreed a bit of mystique means greater currency as a Hollywood power couple. They eventually split in the summer of 2010 shortly after Hudgens commented on how quickly her boyfriend seemed to have grown up: ‘I look at him and I see a man. He was a whole different person.’ Zac has never really spoken of their relationship. Vanessa is now dating actor Austin Butler and Zac spent Valentine’s Day with Mirror Mirror’s Lily Collins – who can’t have been too impressed when a condom fell out of his pocket later that month at The Lorax premiere, or when earlier this month his bare bottom was photo-graphed on the balcony of his harbour-front Sydney hotel room. He was also snapped with his hands down the front of his shorts on the same trip and, during a local TV interview (gone viral), demonstrated how he can unhook a bra with one hand, which he has since repeated on national television in America.

The extra attention can’t hurt as he embarks on a more adult career path, but I’m shocked that his jeans are so low-slung, revealing an expanse of black boxers. Surely an uncovered bottom is the first thing to eradicate if one hopes to be taken seriously. He is nonetheless ridiculously handsome, his military crop long grown out into a neatly tousled quiff with a surferish accent. He’s clean-shaven but not over-preened (those eyebrows have, mercifully, not yet encountered a plucker) and the eyes remain a piercing blue. He has lost much of the bulk he acquired at the film’s bootcamp, having ditched the punishing regime.

I notice a tattoo on his right hand, running along the base of his thumb: YOLO. ‘You Only Live Once,’ he explains. ‘I woke up with it!’ I’m sure he did not. He’s much too sensible. In The Lucky One, Logan sports a tattoo on his back: ‘All glory is fleeting.’ Does the line have a particular resonance? ‘Oh, I love that tattoo. I’m thinking about getting it. I thought it was profound.’